How to analyze the fault of the physical circuit in junior high school?

For a simple circuit, the small bulb does not light up usually: 1, the filament is short-circuited; 2. Filament breaking,When checking with the ammeter, the meter has an indication, indicating that the circuit has current, and the bulb is not lit, there is only a short circuit; If the meter does not indicate the number, the circuit is disconnected.

When checking with a voltmeter, the meter has an indication, and the lamp is not on, the filament is broken; The meter does not show the number, and the other lines of the power supply are good, so there is a short circuit in the filament.

The deflection angle of the meter is small, because the measured data is small, it may be that the data is small, and it is possible that you used the wrong measurement tool, you should use a small range, and use a large range. (For example, to weigh a ring, you should use a small range balance, you use a rod scale). On the contrary, if the deflection angle of the meter is large, and it runs beyond the maximum scale, isn't that the range selected too small?

Elephants can not be used with scales).

The light bulb flickers and flickers because the line is not in good contact, occasionally on, occasionally disconnected.

The sliding rheostat is not connected to one or the other, and both are connected to it, which is equivalent to using the sliding rheostat as a metal rod (wire).

The sliding rheostat does not have the problem of positive and negative binding posts being reversed, and the positive and negative terminals are the same. Ammeter, voltmeter to have the problem of positive and negative wiring, if the connection is reversed, then the pointer is reversed, there is an indication, deflected to the right, and if it is reversed, they will be deflected to the left.

Hehehe, having said all this, I hope it will help you, and I wish you a smooth high school entrance examination (it's 9 years old).

A simple method for physical circuit fault analysis in junior high school, and a common method for judging the connection method of a circuit are as follows:

The component connection characteristic method analyzes the connection mode of the components in the circuit, and the connection is connected in series one by one, and the parallel connection at two points in the circuit is parallel. The current method starts from the positive pole of the power supply and observes the flow of current along the current, if it always flows along a line and returns to the negative pole of the power supply, then the circuit is connected in series.

If the current flows to a certain branch point, divides into branches, flows through the components at each point, converges a point, and finally flows back to the negative pole of the power supply, then the circuit is in parallel. In the component open circuit method, if any element in the circuit is disconnected, there is no current flowing through the other components, the circuit is in series, and if any element in the circuit is disconnected, the other components still have current flowing, the circuit is in parallel.

Characteristic method, if there is a component in the circuit is burned, and the other components can not work, that is, the work of each component in the circuit affects each other and restricts each other, then the circuit is a series circuit, if there is a component in the circuit is burned, other components can still work as usual, that is, the components in the circuit work without affecting each other, then the circuit is a parallel circuit.

In the category of junior high school physics failures, there are three kinds of faults, power short-circuit, local short-circuit, and open circuit.

To determine whether it is a short circuit or an open circuit, the key is whether there is a current, and to observe the light emitting of the bulb or the number of current indications.

There is a current in a local short circuit, and if there is a short circuit in the power supply, the current is too large, and there is no current in the open circuit.

Judge the location of the open circuit, connect a wire in parallel at the place where the open circuit may be broken, and if the open circuit is there, the current will be restored to the other side of the bench bend of the circuit.

To judge the short circuit, connect the upper voltmeter in parallel at the place where the short circuit may be, if there is no indication, the jujube mold indicates that the short circuit is there.

Circuit Failure Analysis Junior High School Physics has:

1. Resistance failure.

1. The voltage indication number is the power supply voltage, the ammeter has no indication (or the deflection is very small), move the slide, and the voltage indication number remains unchanged. (resistor r open).

2. There is no indication of the voltmeter, but there is an indication of the ammeter, and the current indication changes normally when the slide is moved. (Resistor r short circuit).

Second, the sliding rheostat is faulty.

1. The voltmeter and ammeter have an indication, the indication is small, and the moving slide blade changes the voltmeter and current indication number. (The sliding rheostat is connected to the bottom).

2. The voltmeter and ammeter have an indication, the indicator is larger, and the moving slide is moving, and the voltmeter and current indication remain unchanged. (The sliding rheostat is connected as above (or shorted)).

3. There is no indication of voltmeter and ammeter, and the fault is on the sliding rheostat. (Sliding rheostat open circuit).

3. Switch failure.

After connecting the last wire, the ammeter and voltmeter have an indication. (The switch is short-circuited, or the connection circuit switch is not disconnected).

Fourth, the fault is in the voltmeter and ammeter.

1. Close the switch, and the pointers of voltmeter and ammeter are reversed. (The positive and negative binding posts of the two tables are reversed).

2. Close the switch, the deflection amplitude of the voltmeter and ammeter pointer is too large. (The selected range for the two tables is too small).

3. Close the switch, and the deflection amplitude of the pointer of the voltmeter and ammeter is too small. (The selected range of the two tables is too large).

4. Close the switch, the voltmeter is the power supply voltage, the ammeter has no indication number, move the slider, and the voltage indication number remains unchanged. (The positions of the two tables are reversed).

5. Closing switch, voltmeter, ammeter, one of the indicators becomes larger, and the other indicates smaller. (The voltmeter is connected in parallel at both ends of the sliding rheostat).

6. Before closing the switch, the pointers of the voltmeter and ammeter are reversed. (not zeroed).

5. Miscellaneous. There is no indication of voltmeter and ammeter, and the fault is not on the sliding rheostat. (switch open circuit, ammeter open circuit).

Connected to a small range, moving the slide found that both representations were smaller. (The supply voltage is too low).

In junior high school physics, it is common to use ammeter and voltmeter to judge circuit faults, which can be divided into the following situations:

1. The current indication is normal and the voltmeter has no indication number

"Normal current indication number" indicates that the main circuit is the path, and "voltmeter no indication number" indicates that no current passes through the voltmeter, then the cause of the fault may be:

1) The voltmeter is damaged;

2) Poor contact of voltmeter binding post;

3) Short circuit of the electrical appliance connected in parallel with the voltmeter.

2. The voltmeter has an indication but the ammeter has no indication

"The voltmeter has an indicator" indicates that there is a current passing through the voltmeter, and "the ammeter has no indicator" indicates that there is no or almost no current flowing through the ammeter, then the cause of the fault may be:

1) Short circuit of ammeter;

2) The electric appliance connected in parallel with the voltmeter is open, and at this time, a large resistance (voltmeter internal resistance) is connected in series in the circuit where the ammeter is located, so that the current is too small, and the ammeter does not display the number clearly.

3. There is no indication of ammeter and voltmeter

There is no indication in both meters" indicates that there is no current passing through the two meters, in addition to the short circuit of both meters at the same time, the biggest possibility is that the main circuit is open and there is no current.